Electrode forming composition

Abstract

This invention provides an electrode forming composition that can reduce the amount of fluorinated binder used while maintaining battery characteristics. The composition comprises an acidic compound, a hydrogen-bonding compound, a fluorinated binder, a conductive carbon material, and an active substance. The acidic compound is a polymeric organic compound in which the content of acidic groups and / or their salts per molecule is 15% by mass or more, or a non-polymeric organic compound having 4 or more acidic groups and / or their salts in a molecule. The hydrogen-bonding compound is a polymeric organic compound in which the content of acidic groups and / or their salts per molecule is less than 15% by mass, or a non-polymeric organic compound having 3 or fewer acidic groups and / or their salts in a molecule. The content of the acidic compound is 0.001 to 0.5% by mass of the total solids, and the content of the fluorinated binder is 0.01 to 1.0% by mass of the total solids.

Description

Technical Field

[0001] This invention relates to a composition for electrode formation. Prior Technology

[0002] Lithium-ion secondary batteries are currently the most heavily developed type of secondary battery due to their high energy density, high voltage, and lack of memory effect during charging and discharging. As their applications and usage expand, there are increasing demands for lower resistance, longer lifespan, higher capacity, greater safety, and lower cost.

[0003] Lithium-ion rechargeable batteries are prone to degradation due to repeated charging and discharging. Various factors have been reported as mechanisms of degradation, but the main reasons can be cited as follows: degradation of active materials due to trace amounts of residual moisture or electrolyte decomposition inside the battery; increased internal resistance caused by the formation of electrolyte decomposition products; and isolation of active materials due to cracks in the electrode composite material layer (hereinafter also referred to as "electrode layer").

[0004] To address such problems, Non-Patent Literature 1 reports a technique of coating the surface of the positive electrode active material with metal oxides such as Mg, Al, Ti, Sn, Si, and Cu, phosphorus compounds, and carbon. However, it is difficult to say that this can solve the problem of lifespan degradation or the problem of gas generation caused by the decomposition of electrolytes during charging and discharging.

[0005] Furthermore, inorganic compounds containing alkali metal transition metal oxides or transition metal chalcogenides are known as positive electrode active materials for lithium-ion secondary batteries that can achieve a battery voltage of around 4V. Among these, high-nickel positive electrode active materials, represented by LixNiO2, are attractive positive electrode materials with high discharge capacity. However, high-nickel positive electrode active materials have many impurities on their surface, such as residues of raw materials, LiOH formed by proton exchange reactions with water, or Li2CO3 generated by the reaction of LiOH with carbon dioxide in the air.

[0006] In particular, because LiOH is an alkaline component, gelation of the slurry can occur during the manufacturing process of the positive electrode, when mixing the composition containing the positive electrode active material, the binder polyvinylidene fluoride (PVdF), and the solvent N-methyl-2-pyrrolidone (NMP), or when coating the mixed composition. Furthermore, the alkaline component not only corrodes the aluminum commonly used as the positive electrode current collector, increasing the battery's resistance, but also reacts with the electrolyte within the battery, further increasing resistance and potentially becoming a major factor in reduced battery life. On the other hand, Li₂CO₃ decomposes during charging and discharging, producing CO₂ and CO₃ gases. These gases increase the internal pressure of the battery, becoming a major factor in battery swelling and reduced cycle life. Moreover, the increased internal pressure caused by the generated gases also poses a risk of battery damage.

[0007] Therefore, Patent Document 1 reports a method using fluorine gas to treat the positive electrode active material, immobilizing residual LiOH as LiF to prevent gelation and suppress gas generation. However, fluorine gas is highly toxic and difficult to handle, and the LiF generated as a byproduct increases the battery's internal resistance, while the capacity decreases due to corrosion of the positive electrode active material by fluorine gas. Furthermore, residual fluorine reacts with trace amounts of moisture present in the active material or electrolyte to produce hydrogen fluoride, which can easily lead to cycle degradation. []

[0008] Patent document 2 reports a method for removing unreacted lithium hydroxide or impurities from raw materials by washing the positive electrode active material with an aqueous solution containing lithium salt. However, there are issues regarding the environmental impact of the wastewater discharged during washing or the associated costs of its treatment.

[0009] Furthermore, the battery must have sufficiently low resistance. High resistance requires a large voltage to achieve current input and output, making charging and discharging difficult. The resistance of a battery comprises multiple components, broadly categorized as electronic resistance, solution-based ion diffusion resistance, particle-based ion diffusion resistance, and charge movement resistance. Of these, electronic resistance can be relatively easily addressed by adding carbon materials. Furthermore, particle-based ion diffusion resistance can be reduced by decreasing particle size to shorten the diffusion length. On the other hand, reducing charge movement resistance and solution-based ion diffusion resistance is more challenging.

[0010] On the other hand, in applications such as electric vehicles, cost reduction is achieved by thickening the electrodes to reduce the amount of current collector foil used, while simultaneously increasing energy density. However, thickening the electrodes, especially at high current flows, leads to migration or diffusion phenomena caused by the internal electric field within the electrodes. The Li diffusion resistance then becomes a limiting factor for the charge-discharge reaction rate, resulting in a decrease in performance. Furthermore, it induces uneven reactions, accelerating degradation. Therefore, there is a strong desire to reduce the ion diffusion resistance in the solution. Although electrolytes and additives have been developed with the aim of reducing Li diffusion resistance in the electrolyte, none have yet demonstrated sufficiently satisfactory performance.

[0011] Patent document 3 reports on the use of lithium salt structures Compounds containing (-M-Li+) polymerizable groups are used in electrodes or electrolytes. The -M- group, calculated using density functional theory (B3LYP / 6-31G(d)), has a lithium-ion coordination energy of 100-1500 kJ / mol. These compounds form a lithium-ion-coordinating polymeric film on the surface of the active material, reducing the desolvation energy of the main resistive component within the charge-movement resistance. However, the use of large amounts of polyvinylidene fluoride (PVDF) and the addition of these compounds significantly increases the Li diffusion resistance, failing to adequately reduce the overall resistance.

[0012] In Patent Document 4, the low-temperature characteristics of a battery are improved by controlling the proportion of ethyl carbonate in a mixed solvent containing ethyl carbonate and chain carbonates in a non-aqueous electrolyte for secondary batteries, which is composed of a non-aqueous solvent and lithium salt. Simultaneously, an electrolyte containing a compound with intramolecular SF bonds, such as a sulfonyl fluoride or fluorosulfonate compound, is used. This is believed to be because suppressing the content of high-viscosity ethyl carbonate improves the permeability of the electrode composite layer, allowing for sufficient diffusion and penetration of the electrolyte. However, reducing the content of highly polar ethyl carbonate may decrease the dissociation of the electrolyte, thus it may not be the best approach.

[0013] Non-patent literature 2: Journal of The Electrochemical Society, 165 (5) A1027-A1037 (2018) reports that the use of methyl acetate increases ionic conductivity and improves charge-discharge characteristics. However, the degradation of the battery is accelerated, and complex additive technologies or high-cost active materials are required, which has not yet been resolved.

[0014] Furthermore, in battery manufacturing, there is a strong desire to reduce costs or minimize environmental impact. This requires the use of inexpensive materials with stable supply, materials with low process overhead, or materials used in smaller quantities. [Previous Technical Documents] [Patent Literature]

[0015] [Patent Document 1] Japanese Patent Application Publication No. 2006-286240 [Patent Document 2] International Publication No. 2017 / 034001 [Patent Document 3] International Publication No. 2013 / 002186 [Patent Document 4] Japanese Patent Application Publication No. 2019-117811 [Non-patent literature]

[0016] [Non-patent literature 1] Journal of Alloys and Compounds 706 (2017) 24-40 [Non-Patent Literature 2] Journal of The Electrochemical Society, 165 (5) A1027-A1037 (2018) Summary of the Invention

[0017] [The problem that the invention aims to solve]

[0018] Based on the above situation, and with the aim of reducing the aforementioned resistance, the formulation of the electrode forming composition was reviewed. It was found that by combining specific acid-containing compounds, specific hydrogen-bonding compounds, and a small amount of fluorine-based binders, an electrode with low charge-movement resistance and high ion diffusion can be manufactured. The aim is to provide an electrode forming composition that can reduce the amount of fluorine-based binder used while maintaining good stability and improving battery characteristics. [Methods for solving the problem]

[0019] To achieve the above-mentioned objectives, the inventors have repeatedly and diligently examined the material and discovered that, in an electrode-forming composition comprising an acid-containing compound, a hydrogen-bonding compound, a fluorinated binder, a conductive carbon material, and an active material, the acid-containing compound is used in a specific amount of a polymeric organic compound having an acidic group and / or its salt content of 15% by mass or more per molecule, or a non-polymeric organic compound having 4 or more acidic groups and / or their salts in the molecule. Furthermore, the hydrogen-bonding compound is used by combining a polymeric organic compound having an acidic group and / or its salt content of less than 15% by mass per molecule, or a non-polymeric organic compound having 3 or fewer acidic groups and / or their salts in the molecule. This allows for a reduction in the amount of fluorinated binder used, a decrease in the diffusion resistance of metal ions such as Li, and maintenance of battery characteristics, thus completing the present invention.

[0020] That is, the present invention provides the following composition for electrode formation. 1. A composition for forming an electrode, comprising an acidic compound, a hydrogen-bonding compound, a fluorinated binder, a conductive carbon material, and an active substance. The aforementioned compounds containing acidic groups are either polymeric organic compounds in which the content of acidic groups and / or their salts per molecule is 15% by mass or more, or non-polymeric organic compounds in which the molecule has 4 or more acidic groups and / or their salts. The aforementioned compounds containing hydrogen-bonded groups are either polymeric organic compounds in which the content of acidic groups and / or their salts per molecule is less than 15% by mass, or non-polymeric organic compounds in which the molecule has three or fewer acidic groups and / or their salts. The content of the above-mentioned acid-containing compounds is 0.001~0.5% by mass of the total solids. The content of the above-mentioned fluorinated binder is 0.01~1.0% by mass of the total solids. 2. The electrode forming composition as described in 1, wherein the content of the above-mentioned fluorine-based binder is 0.1 to 0.7% by mass of the total solids. 3. The electrode forming composition as in 1 or 2, wherein the content of the above-mentioned acid-containing compound is 0.01 to 0.3% by mass of the total solids. 4. An electrode forming composition as described in any one of 1 to 3, wherein the content of the aforementioned hydrogen-bonded compound is 0.001 to 0.5% by mass of the total solids. 5. The electrode forming composition of any one of 1 to 4, wherein the above-mentioned acid-containing compound is a polymeric organic compound in which the content of acidic group and / or its salt per molecule is 25% by mass or more, or a non-polymeric organic compound having 5 or more acidic groups and / or their salts in the molecule. 6. An electrode forming composition as described in any one of 1 to 5, wherein the acidic group and its salt are selected from at least one group consisting of carboxylic acid group, phosphoric acid group, sulfonic acid group and salts thereof. 7. The electrode forming composition as described in 6, wherein the above-mentioned acidic group and its salt are carboxylic acid groups and / or their salts. 8. The electrode forming composition of any one of 1 to 7, wherein the above-mentioned acid-containing compound is a polymeric organic compound. 9. The electrode forming composition of 8, wherein the weight average molecular weight of the acid-containing compound is 250 to 2,000,000. 10. An electrode forming composition as described in any one of 1 to 9, wherein the aforementioned hydrogen-bonding compound is selected from at least one group consisting of compounds containing carbonyl groups, hydroxyl groups, ether groups, amine groups, and sulfonyl groups. 11. The electrode-forming composition of 10, wherein the aforementioned hydrogen-bonding compound is selected from at least one of the following: The polymeric organic compounds selected from the group consisting of polylactic acid, maleic anhydride polymers, anhydrous maleimide polymers, polyphenols, polyvinyl alcohol, polyethylene glycol, polyethyleneimine, polyether ether, polyether ether and polyaryl ether ether, and copolymers containing at least one of these and derivatives thereof, and Nonpolymeric organic compounds selected from the group consisting of maleic anhydride, acetone, citric acid, tannic acid, diethyl ether, tetrahydrofuran, amino acids alanine, aspartic acid, aspartic acid, glutamic acid, serine, arginine, cysteine, glutamic acid, glycine, proline, tyrosine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, sulfonic acid halides, triethylene glycol dimethyl sulfonate, and ethyl p-toluenesulfonate. 12. The electrode forming composition as described in 11, wherein the hydrogen-bonded compound is a polymeric organic compound selected from the group consisting of polylactic acid, maleic anhydride polymer, anhydrous maleimide polymer and polyvinyl alcohol, and copolymers and derivatives thereof containing at least one of the above. 13. The electrode forming composition of 8 or 9, wherein the acidic compound is a copolymer comprising the following repeating units: repeating units derived from monomers having a group selected from the group consisting of aromatic rings, alkyl, amino, ether, nitrile, hydroxyl and carbonyl groups, and repeating units derived from monomers having a carboxylic acid group and / or its salt. 14. The electrode forming composition of 13, wherein the acidic compound is a copolymer comprising the following repeating units: repeating units derived from monomers having groups selected from the group consisting of nitrile, hydroxyl and carbonyl groups, and repeating units derived from monomers having carboxylic acid groups and / or their salts. 15. An electrode forming composition as described in any one of 1 to 14, wherein the weight average molecular weight of the fluorinated binder is 600,000 to 3,000,000. 16. An electrode forming composition as described in any of 1 to 15, wherein the heat of fusion of the fluorine-based binder, as determined by differential scanning calorimeter (DSC), is 10 to 35.8 J / g. 17. An electrode forming composition as described in any of 1 to 16, wherein the fluorine-based binder is modified with a polar functional group. 18. An electrode forming composition as described in any of 1 to 17, further comprising a dispersant. 19. The electrode forming composition of 18, wherein the dispersant is a homopolymer of monomers selected from the group consisting of nitrile monomers, aromatic olefin monomers and aliphatic olefin monomers, or a copolymer of two or more such monomers, and the weight average molecular weight is 1,000 to 2,000,000. 20. The electrode forming composition of 18 or 19, wherein the content of the above dispersant is 0.01 to 0.5% by mass of the total solids. 21. An electrode forming composition as described in any one of 1 to 20, wherein the active material is an oxide containing Li and at least one selected from Ni and Fe, or contains S, and the electrode forming composition is a composition for a positive electrode. 22. For any of the electrode-forming components in 1 to 21, the loss modulus of dynamic viscoelasticity is greater than the storage modulus after immediate modulation and after standing at 25°C for 3 hours. 23. An electrode having a current collector substrate and an electrode composite material layer formed on at least one side of the current collector substrate, wherein the electrode composite material layer is formed with an electrode forming composition as described in any one of 1 to 22. 24. An energy storage device having electrodes as shown in 23. 25. The energy storage device, such as 24, is an all-solid-state battery. [The effects of the invention]

[0021] The electrode forming composition of the present invention can be applied to form electrodes for energy storage devices. Energy storage devices with electrodes made using this composition can expect advantages such as: reduced diffusion resistance of metal ions such as Li due to reduced use of fluorine-based binders (improved battery performance) or reduced cost; longer lifespan due to improved reaction uniformity; reduced environmental impact; reduced solvent usage or shortened drying time due to high solids content in the slurry; and also the ability to suppress degradation due to the neutralization effect of the alkaline components caused by the addition of organic compounds with acidic groups.

[0022] Regarding the neutralization of alkaline components, although the mechanism by which it manifests is not clear, it is believed that by using specific acidic compounds as electrode additives, alkaline impurities can be neutralized. Furthermore, the neutralized carboxylates and the like are insoluble in the electrode paste and can therefore be fixed on the surface of the active material. Regarding the diffusion resistance of metal ions, compared to the amount of commonly used fluorine-based binders which is on the order of several mass percent in the electrode, in this electrode, which uses specific acid-containing compounds and specific hydrogen-bonding compounds as electrode additives, the necessary amount can be as low as 1 mass percent or less. Therefore, it is believed that the organic components that would hinder the diffusion of metal ions such as Li in the electrode can be significantly reduced. Furthermore, significantly reducing the use of fluorine-based binders means lower battery manufacturing costs and a reduced environmental impact. It is also expected to improve electrode cycle life, extend battery life, and enhance safety. Simple Explanation of the Diagram

[0023] [Figure 1] is a partial NMR spectrum of the fluorinated binder Solef 5140. [Figure 2] is a partial NMR spectrum of the fluorinated binder Solef 5130. Implementation

[0024] [Forms of Invention]

[0025] The electrode forming composition of the present invention comprises an acidic compound, a hydrogen-bonding compound, a fluorinated binder, a conductive carbon material, and an active substance. The acidic compound is a polymeric organic compound in which the content of acidic group and / or its salt per molecule is 15% by mass or more, or a non-polymeric organic compound having 4 or more acidic groups and / or their salts in a molecule. The hydrogen-bonding compound is a polymeric organic compound in which the content of acidic group and / or its salt per molecule is less than 15% by mass, or a non-polymeric organic compound having 3 or fewer acidic groups and / or their salts in a molecule. The content of the acidic compound is 0.001 to 0.5% by mass of the total solids, and the content of the fluorinated binder is 0.01 to 1.0% by mass of the total solids.

[0026] In this invention, the term "polymer type organic compound" refers to an organic compound formed by the polymerization of a plurality of monomers, and the term "non-polymer type organic compound" refers to an organic compound other than the aforementioned polymer type organic compound.

[0027] When the aforementioned acid-containing compound is a polymeric organic compound, the content of acidic groups and / or their salts per molecule is 15% by mass or more, preferably 25% by mass or more. Furthermore, when it is a non-polymeric organic compound, it is preferable to have 4 or more acidic groups and / or their salts in the molecule, or 5 or more acidic groups and / or their salts in the molecule. There is no particular upper limit to the content of acidic groups and / or their salts, but when it is a polymeric organic compound, it is preferable to have 85% by mass or less per molecule, and when it is a non-polymeric organic compound, it is preferable to have 12 or less per molecule. From the viewpoint of improving electrode strength, the aforementioned acid-containing compound is preferably a polymeric organic compound.

[0028] From a cost and availability perspective, the aforementioned acidic groups are preferably carboxylic acid groups, phosphate groups, or sulfonic acid groups, with carboxylic acid groups being more preferred. Examples of salts of carboxylic acid groups, phosphate groups, or sulfonic acid groups include alkali metal salts such as sodium and potassium; group II metal salts such as magnesium and calcium; ammonium salts; aliphatic amine salts such as propylamine, dimethylamine, triethylamine, and ethylenediamine; alicyclic amine salts such as imidazoline, piperazine, and morpholine; aromatic amine salts such as aniline and diphenylamine; and pyridinium salts. Based on the same viewpoint, alkali metal salts are preferred, with lithium salts being more preferred. These acidic groups and their salts may contain one type or two or more types.

[0029] Specific examples of polymeric organic compounds containing acidic groups include polyacrylic acid, polyic acid, polymaleic acid, polyfumaric acid, polymethacrylic acid, poly(vinyl sulfonic acid), poly(4-styrene sulfonic acid), alginic acid, or polysaccharides such as cellulose, phosphorus oxides, and salts thereof, with polyacrylic acid, polyic acid, polymaleic acid, and salts thereof being more preferred.

[0030] Furthermore, the aforementioned polymer can also be a copolymer. As a specific example, a copolymer comprising repeating units derived from monomers having groups selected from the group consisting of aromatic rings, alkyl, amino, ether, nitrile, hydroxyl and carbonyl groups, and repeating units derived from monomers having carboxylic acid groups and / or their salts. Preferably, a copolymer comprising repeating units derived from monomers having groups selected from the group consisting of nitrile, hydroxyl and carbonyl groups, and repeating units derived from monomers having carboxylic acid groups and / or their salts.

[0031] Examples of aromatic rings mentioned above include benzene rings, biphenyl rings, naphthalene rings, anthracene rings, and phenanthrene rings. The alkyl group described above is preferably a straight-chain, branched, or cyclic alkyl group having 1 to 6 carbon atoms. Specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tributyl, n-pentyl, isopentyl, neopentyl, n-hexyl, cyclopentyl, and cyclohexyl.

[0032] The average molecular weight of the aforementioned polymeric organic compounds is not particularly limited, but the weight average molecular weight (Mw) is preferably 250~2,000,000, more preferably 1,000~1,000,000, and even more preferably 1,000~250,000. Furthermore, Mw is a polystyrene conversion value determined by gel permeation chromatography (GPC).

[0033] Examples of non-polymeric organic compounds containing acidic groups include compounds with four or more carboxylic acid groups, phosphoric acid groups, or sulfonic acid groups in their molecules. Examples of compounds containing carboxylic acid groups include aromatic carboxylic acids, alicyclic carboxylic acids, and aliphatic carboxylic acids.

[0034] Specific examples of compounds having four carboxylic acid groups include aromatic tetracarboxylic acids such as benzopyrene, 3,3',4,4'-biphenyltetracarboxylic acid, 3,3',4,4'-benzophenone tetracarboxylic acid, 3,3',4,4'-diphenyl ether tetracarboxylic acid, and 3,3',4,4'-diphenyl tannic acid tetracarboxylic acid; alicyclic tetracarboxylic acids such as 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,3,4-cyclohexanetetracarboxylic acid, and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthous succinic acid; and aliphatic tetracarboxylic acids such as 1,2,3,4-butanetetracarboxylic acid.

[0035] Specific examples of compounds having five carboxylic acid groups include aromatic pentacarboxylic acids such as benzenepentacarboxylic acid and 1,2,4,5,8-naphthalenepentacarboxylic acid; and alicyclic pentacarboxylic acids such as 1,2,3,4,5-cyclohexanepentacarboxylic acid and diethylenetriaminepentaacetic acid.

[0036] Specific examples of compounds having six carboxylic acid groups include aromatic hexacarboxylic acids such as benzenehexacarboxylic acid and [1,1':4',1”-triphenyl]-2',3,3”,5,5',5”-hexacarboxylic acid; alicyclic hexacarboxylic acids such as cyclohexanehexacarboxylic acid and 1,2,3,4,5,7-naphthalenehexacarboxylic acid; and aliphatic hexacarboxylic acids such as 1,8,9,10,11,18-octanehexacarboxylic acid and 1,4,5,6,7,10-decanehexacarboxylic acid.

[0037] Specific examples of compounds having seven carboxylic acid groups include aliphatic heptacarboxylic acids such as 4,6-bis(carboxymethyl)-1,2,4,6,11-tetanepentacarboxylic acid and 1,8,9,10,11-heptadecanepentacarboxylic acid.

[0038] Specific examples of compounds having eight carboxylic acid groups include aromatic octacarboxylic acids such as [1,1'-biphenyl]-2,2',3,3',5,5',6,6'-octacarboxylic acid and [1,1':4',1”-triphenyl]-2',3,3',3”,5,5',5”,6'-octacarboxylic acid; and aliphatic octacarboxylic acids such as 9-hydroxy-9-methyl-1,2,3,4,5,6,7,8-pentadecanoctacarboxylic acid, 1,2,3,4,5,6,7,8-octaneoctacarboxylic acid and 1,3,9,15,21,27,33,39-nonadecanoctacarboxylic acid.

[0039] Specific examples of compounds having four phosphate groups include tetraphosphate and N,N,N',N'-ethylenediaminetetra(methylenephosphonic acid).

[0040] Specific examples of compounds having five phosphate groups include pentaphosphate and phytic acid.

[0041] Specific examples of compounds having six phosphate groups include hexaphosphate, etc.

[0042] Specific examples of compounds having four sulfonic acid groups include tetrasulfonic phthalocyanine and biphenyl tetrasulfonic acid.

[0043] The above-mentioned compounds containing acidic groups can be used alone or in combination of two or more.

[0044] The content of the aforementioned acid-containing compound is 0.001 to 0.5% by mass of the total solids, preferably 0.001 to 0.3% by mass, and more preferably 0.001 to 0.2% by mass. By setting the content of the acid-containing compound within the above range, the amount of fluorine-based binder used later can be reduced, and the battery characteristics of the resulting battery can be maintained. Furthermore, in this invention, the term "solids" refers to components other than the solvent constituting the composition (hereinafter, the same applies).

[0045] From the viewpoint of cost and availability, examples of hydrogen-bonding groups include carbonyl, hydroxyl, ether, amino, and sulfonyl groups, with carbonyl and hydroxyl groups being preferred. These hydrogen-bonding groups may include one type or two or more types.

[0046] The above-mentioned compounds containing hydrogen-bonded groups may also contain acidic groups, but when they are polymeric organic compounds, the content of acidic groups and / or their salts per molecule is less than 15% by mass; when they are non-polymeric organic compounds, they have 3 or fewer acidic groups and / or their salts in the molecule.

[0047] Specific examples of polymeric organic compounds containing hydrogen-bonded groups include polylactic acid, maleic anhydride polymers, anhydrous maleimide polymers (carbonyl compounds); polyphenols, polyvinyl alcohol (hydroxyl compounds); polyethylene glycol (ether compounds); polyethyleneimine (amine compounds); polyether tin, polytin, polyaryl tin (sulfonyl compounds), and copolymers containing at least one of these and their derivatives.

[0048] When the aforementioned polymeric organic compounds containing hydrogen-bonded groups are copolymers, in addition to repeating units derived from the raw material monomers of the aforementioned polymers, they may also contain repeating units derived from other monomers such as isobutylene. In this invention, a copolymer of isobutylene and maleic anhydride is preferred. The copolymer of isobutylene and maleic anhydride can react with trace amounts of moisture in the electrode paste through the portion derived from the carboxylic anhydride, reducing the water content, and the copolymer's high oxidation resistance due to the portion derived from isobutylene can be cited as a preferred reason.

[0049] The average molecular weight of the above-mentioned polymeric organic compounds is not particularly limited, but the weight average molecular weight (Mw) is preferably 250 to 2,000,000, more preferably 1,000 to 1,000,000, and even more preferably 1,000 to 250,000.

[0050] Specific examples of non-polymeric organic compounds containing hydrogen-bonded groups include maleic anhydride, acetone, citric acid (carbonyl compounds); tannic acid (hydroxyl compounds); diethyl ether, tetrahydrofuran (ether compounds); alanine, aspartic acid, asparagine, glutamic acid, serine, arginine, cysteine, glutamine, glycine, proline, tyrosine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine (amine compounds); sulfonic acid halides, triethylene glycol dimethyl sulfonate, ethyl p-toluenesulfonate (sulfonyl compounds), maleic anhydride, citric acid, and tannic acid.

[0051] Specific examples of the aforementioned sulfonic acid halides include chlorides, bromides, and iodides of organic sulfonic acids such as benzenesulfonic acid, p-toluenesulfonic acid, 4-bromobenzenesulfonic acid, 4-methoxybenzenesulfonic acid, 4-benzyloxybenzenesulfonic acid, 1-naphthylsulfonic acid, 2-naphthylsulfonic acid, 1,3-benzenedisulfonic acid, methanesulfonic acid, and ethanesulfonic acid. The above-mentioned organic sulfonic acid halides can be synthesized by general methods such as reacting organic sulfonic acids with halogenating agents, or commercially available products can be used.

[0052] The above-mentioned compounds containing hydrogen-bonded groups can be used alone or in combination of two or more.

[0053] The content of the aforementioned hydrogen-bonding compound is 0.001~0.5% by mass of the total solids, preferably 0.001~0.3% by mass, and more preferably 0.001~0.2% by mass. By setting the content of the hydrogen-bonding compound within the above range, the amount of fluorine-based binder used later can be reduced, and the battery characteristics of the resulting battery can be maintained. Furthermore, the storage stability of the composition can be improved.

[0054] As for the aforementioned fluorinated adhesives, suitable materials can be selected from well-known sources without particular limitation. However, specific examples include copolymers containing at least one monomer selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene, vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene. Furthermore, the aforementioned fluorinated adhesives can be modified with polar functional groups. Moreover, the aforementioned polar functional groups can be identified by the presence or absence of a distinct peak in the range of 10-15 ppm during nuclear magnetic resonance (NMR) measurements. As specific examples of NMR spectra, Figure 1 shows the NMR spectrum of Solef 5140 PVdF manufactured by SOLVAY, and Figure 2 shows the NMR spectrum of Solef 5130.

[0055] The weight average molecular weight (Mw) of the aforementioned fluorinated binder, from the perspective of improving the adhesion between the current collector and the electrode layer, is preferably 600,000 to 3,000,000, more preferably 700,000 to 2,000,000, even more preferably 700,000 to 1,500,000, and even more preferably 700,000 to 1,300,000.

[0056] The aforementioned fluorinated binder has a heat of fusion of preferably 10~35.8 J / g, more preferably 15~35.5 J / g, even more preferably 20~35.5 J / g, and even more preferably 25~35.5 J / g, as determined by differential scanning calorimetry (DSC). Using a fluorinated binder with a heat of fusion within the above range improves the adhesion between the current collector and the electrode layer.

[0057] The content of the aforementioned fluorinated binder is 0.01 to 1.0% by mass of the total solids, preferably 0.05 to 0.6% by mass, more preferably 0.1 to 0.7% by mass, even more preferably 0.2 to 0.7% by mass, and even more preferably 0.3 to 0.6% by mass. If the content of the fluorinated binder is too high, the composition may gel and become unusable.

[0058] There are no particular limitations on conductive carbon materials. Suitable materials can be selected from well-known conductive carbon materials such as carbon black, Ketjen black, acetylene black (AB), carbon whiskers, carbon nanotubes (CNT), carbon fibers, natural graphite, and artificial graphite. However, from the point of view of conductivity, dispersibility, and availability, AB and CNT are preferred.

[0059] CNTs are generally fabricated using methods such as arc discharge, chemical vapor deposition (CVD), and laser ablation. However, the CNTs used in this invention can be obtained by any method. Furthermore, CNTs include single-layer CNTs (hereinafter referred to as SWCNTs) formed by rolling a single carbon film (graphene sheet) into a cylindrical shape, two-layer CNTs (hereinafter referred to as DWCNTs) formed by rolling two graphene sheets into concentric circles, and multi-layer CNTs (MWCNTs) formed by rolling multiple graphene sheets into concentric circles. However, in this invention, SWCNTs, DWCNTs, and MWCNTs can be used individually or in combination in multiples.

[0060] Furthermore, when producing SWCNTs, DWCNTs, or MWCNTs using the above methods, catalyst metals such as nickel, iron, cobalt, and yttrium may remain, necessitating purification to remove these impurities. Acid treatment with nitric acid, sulfuric acid, etc., combined with ultrasonic treatment, is effective for impurity removal. However, acid treatment with nitric acid, sulfuric acid, etc., may disrupt the π-conjugated system constituting CNTs, potentially damaging the original properties of CNTs. Therefore, purification under appropriate conditions is desirable for their use.

[0061] Specific examples of CNTs that can be used in this invention include: Super Gloss CNTs [manufactured by the National Research and Development Corporation New Energy & Industrial Technology Development Organization], eDIPS-CNTs [manufactured by the National Research and Development Corporation New Energy & Industrial Technology Development Organization], SWNT series [manufactured by Meijo Nano Carbon Co., Ltd.], VGCF series [manufactured by Showa Denko Co., Ltd.], FloTube series [manufactured by CNano Technology Co., Ltd.], AMC [manufactured by Ube Industries Co., Ltd.], NANOCYL NC7000 series [manufactured by Nanocyl SA Co., Ltd.], Baytubes [manufactured by Bayer Co., Ltd.], GRAPHISTRENGTH [manufactured by ARKEMA Co., Ltd.], MWNT7 [manufactured by Hodogaya Chemical Co., Ltd.], and Hypeprion CNTs [Hypeprion Catalysis CNTs]. [International Corporation: Product Name], TC series [Toda Kogyo (Co., Ltd.: Product Name], FloTube series [Jiangsu Cnano Technology Corporation: Product Name], LUCAN BT1003M [LG Chem. Ltd.: Product Name], etc.

[0062] The content of the aforementioned conductive carbon material is not particularly limited, but it is preferably 0.1 to 4.0% by mass of the total solids, and more preferably 0.5 to 3.0% by mass. By setting the content of the conductive carbon material within the above range, good electrical conductivity can be obtained.

[0063] As the active material, various active materials conventionally used in energy storage devices such as secondary batteries can be used. However, in this invention, active materials for positive electrodes can be appropriately used. As the positive electrode active material, for example, in the case of lithium secondary batteries or lithium-ion secondary batteries, chalcogenides capable of adsorbing and desorbing lithium ions, lithium-ion-containing chalcogenides, polyanionic compounds, elemental sulfur and their compounds, etc., can be used.

[0064] Examples of chalcogenides that can be adsorbed and desorbed include FeS₂, TiS₂, MoS₂, V₂O₆, V₆O₁₃, and MnO₂. Examples of lithium-ion-containing chalcogenides include LiCoO₂, LiMnO₂, LiMn₂O₄, LiMo₂O₄, LiV₃O₈, LiNiO₂, LiₓNi₂M₁₁₀ ... 2 indicates that at least one species is selected from the group consisting of Zr, Ti, Mg, W and V, such as 1.00≦a≦1.50, 0.00≦x≦0.50, 0≦y≦0.50, 0.000≦z≦0.020, 0.000≦w≦0.020, etc. Examples of polyanionic compounds include LiFePO4. Examples of sulfur compounds include Li₂S and erythramine. These active substances can be used alone or in combination of two or more.

[0065] In this invention, among the above-mentioned positive electrode active materials, it is preferred to include an oxide containing Li and at least one selected from Ni and Fe, or to include S, namely FeS 2, TiS 2, MoS 2, LiNiO 2, Li xNi yM 1-yO 2 (M represents at least one or more metallic elements selected from Co, Mn, Ti, Cr, V, Al, Sn, Pb and Zn, 0.05≦x≦1.10, 0.3≦y≦1.0), Li aNi (1-xy )Co xM 1 yM 2 zX wO 2 (M 1 represents at least one element selected from the group consisting of Mn and Al, M 2 indicates at least one of the following groups selected from Zr, Ti, Mg, W and V: 1.00≦a≦1.50, 0.00≦x≦0.50, 0≦y≦0.50, 0.000≦z≦0.020, 0.000≦w≦0.020), LiFePO4, Li2S, and erythramine.

[0066] The content of the above-mentioned active substances is preferably 94.000~99.888% by mass of the total solids, and more preferably 95.0~99.0% by mass.

[0067] Furthermore, the electrode forming composition of the present invention may also include binders other than fluorinated binders, without impairing the effects of the present invention. Other adhesives can be suitably selected from well-known materials without particular limitation, but non-aqueous adhesives are more suitable for use in this invention. Specific examples include polyimide, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, polyethylene, and polypropylene. These can be used alone or in combination of two or more.

[0068] When other binders mentioned above are included, their content is not particularly limited, but it is preferably less than 5.0% by mass of the total solids content, more preferably less than 3.0% by mass, even more preferably less than 3.0% by mass, and most preferably not included.

[0069] In the electrode forming composition of the present invention, a dispersant may be included to further improve the dispersibility of the aforementioned conductive carbon material or active material. As the dispersant, suitable options are available from those conventionally used as dispersants for conductive carbon materials such as CNTs; however, from the perspective of battery stability, a nonionic polymer is preferred. Examples of nonionic polymers include polyvinylpyrrolidone (PVP) and polymers having at least one group selected from the group consisting of nitrile, carbonyl, sulfonyl, phenyl (aromatic ring), and ether groups.

[0070] In this invention, the preferred monomers are homopolymers of polyvinylpyrrolidone (PVP) and monomers selected from the group consisting of nitrile monomers, aromatic olefin monomers and aliphatic olefin monomers, or copolymers of two or more of these monomers.

[0071] Examples of nitrile monomers include acrylonitrile, 2-methylenepentanedionitrile, and trans-butenedionitrile.

[0072] Examples of aromatic olefin monomers include styrene, vinyl biphenyl, and vinyl pyridine.

[0073] Examples of aliphatic olefin monomers include butadiene, isobutylene, and propylene.

[0074] Specific examples of the aforementioned polymers include polyacrylonitrile, polyester, polyimide, styrene, acrylonitrile / styrene copolymer, acrylonitrile / butadiene copolymer, etc., with polyacrylonitrile being preferred.

[0075] The above dispersants can be used alone or in combination of two or more.

[0076] The average molecular weight of the above dispersant is not particularly limited, but the weight average molecular weight (Mw) is preferably 1,000 to 2,000,000, more preferably 1,000 to 1,000,000, and even more preferably 1,000 to 250,000.

[0077] When the above-mentioned dispersant is included, its content is not particularly limited, but it is preferably 0.01 to 0.5% by mass of the total solids, more preferably 0.01 to 0.3% by mass, and even more preferably 0.01 to 0.2% by mass.

[0078] Furthermore, when the above-mentioned acid-containing compound or the above-mentioned hydrogen-bonded compound functions as a dispersant, one or all of the above-mentioned dispersant is replaced with the above-mentioned acid-containing compound and / or the above-mentioned hydrogen-bonded compound.

[0079] Solvents can also be used in the preparation of compositions for electrode formation. As a solvent, there are no particular limitations as long as it is one that has been used in the preparation of compositions for electrode formation in the past. Examples include water; ethers such as 1,2-dimethoxyethane (DME); halogenated hydrocarbons such as dichloromethane, chloroform, and 1,2-dichloroethane; acetamides such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP); ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; methanol, ethanol, and n-propanol. Alcohols such as isopropanol, n-butanol, and tributanol; aliphatic hydrocarbons such as n-heptane, n-hexane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; glycol ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether; glycols such as ethylene glycol and propylene glycol; carbonates such as ethyl carbonate, propyl carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; and organic solvents such as γ-butyrolactone, dimethyl sulfoxide (DMSO), dioxolane, and cyclobutane. These solvents can be used alone or in combination of two or more.

[0080] Furthermore, when using the above-mentioned fluorinated adhesives and other adhesives as needed, they can be dissolved or dispersed in such solvents as required. Suitable solvents for this situation include water, NMP, DMSO, ethyl acetate, propyl acetate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, THF, dioxolane, cyclobutane, DMF, and DMAc. The appropriate solvent should be selected according to the type of adhesive. However, for non-water-soluble adhesives such as PVdF, NMP is preferred, while for water-soluble adhesives, water is preferred.

[0081] The concentration of solid components in the electrode forming composition of the present invention is appropriately set considering factors such as the coatability of the composition or the thickness of the formed film, but it is usually about 50 to 90% by mass, preferably about 60 to 88% by mass, and even more preferably about 70 to 85% by mass.

[0082] In the electrode forming composition of the present invention, the loss modulus of elasticity measured by dynamic viscoelasticity is preferably greater than the storage modulus of elasticity. By setting the loss modulus of elasticity to be greater than the storage modulus of elasticity, an electrode forming composition with good coatability can be obtained. Furthermore, from the viewpoint of coatability, the lower limit of the loss modulus of elasticity of the above-mentioned electrode forming composition is preferably 1 Pa or more. On the other hand, based on the same viewpoint, the upper limit of the loss modulus of elasticity of the above-mentioned electrode forming composition is preferably 1,000 Pa or less, more preferably 100 Pa or less, and even more preferably 50 Pa or less. Furthermore, the loss modulus and storage modulus of dynamic viscoelasticity (frequency-dependent measurement) were measured at 25°C within a strain range of 0.1% to 1,000% and a shear rate range of 0.00628 to 62.9 (1 / s). In this invention, the magnitude of the loss modulus and storage modulus was determined using the loss modulus and storage modulus measured immediately after modulation and after standing at 25°C for 3 hours. At that time, the measured value at 0.1% strain was used.

[0083] In this invention, the loss modulus of elasticity measured by dynamic viscoelasticity is preferably greater than the storage modulus of elasticity immediately after modulation and after standing at 25°C for 3 hours. Furthermore, the rate of change of the storage modulus of elasticity and the loss modulus of elasticity measured by dynamic viscoelasticity is preferably less than 300% from immediately after modulation to after standing at 25°C for 3 hours.

[0084] The electrode forming composition of the present invention can be obtained by mixing the above-mentioned components at a specific temperature. Furthermore, when including any component other than the additives and active substances of the present invention, the additives and active substances can be mixed together with any component, or they can be mixed with any component after the two components have been pre-mixed. In either method, the effects of the present invention can be fully manifested by coating the surface of the active substance with the additives.

[0085] The electrode of the present invention has an electrode layer formed by the electrode forming composition described above on at least one side of the substrate of the current collector. Methods for forming an electrode layer on a substrate include a method that does not use solvents, by pressing a prepared electrode forming composition onto the substrate (dry method), and a method that uses solvents, prepares the electrode forming composition, coats it onto the substrate, and then dries it (wet method). These methods are not particularly limited, and various conventional methods can be used. For example, wet methods include various printing methods such as offset printing and screen printing, blade coating, dip coating, spin coating, bar coating, slot coating, inkjet coating, and die coating.

[0086] Furthermore, regarding the heating and drying process, either natural drying or heating and drying can be used, but from the perspective of production efficiency, heating and drying is preferred. When carrying out heating and drying, the preferred temperature is around 50~400℃, and more preferably around 70~150℃.

[0087] Examples of substrates used for the aforementioned electrodes include metal substrates made of platinum, gold, iron, stainless steel, copper, aluminum, lithium, etc.; alloy substrates made of any combination of these metals; oxide substrates made of indium tin oxide (ITO), indium zinc oxide (IZO), antimony tin oxide (ATO), etc.; and carbon substrates made of glassy carbon, pyrolytic graphite, carbon felt, etc. In particular, the thickness of the substrate is not particularly limited, but in this invention, it is preferably 1 to 100 μm.

[0088] The thickness of the electrode layer is not particularly limited, but it is preferably about 0.01 to 1,000 μm, and more preferably about 5 to 300 μm. Furthermore, when the electrode layer is used as an electrode on its own, its thickness is preferably 10 μm or more.

[0089] The electrode system can be pressurized as needed. Commonly used methods can be used for pressurization, but mold pressing or roller pressing is particularly preferred. Furthermore, there is no particular limitation on the pressurization pressure, but it is preferably 1 kN / cm or higher, more preferably 2 kN / cm or higher, and especially preferably 5 kN / cm or higher. Also, there is no particular limitation on the upper limit of the above pressurization pressure, but it is preferably 50 kN / cm or lower.

[0090] The secondary battery of the present invention comprises the aforementioned electrodes, and more specifically, is composed of at least one pair of positive and negative electrodes, a separator and an electrolyte situated between the electrodes, wherein at least one of the positive and negative electrodes is composed of the aforementioned electrodes. Other battery components may be used by selecting appropriate components from those already known.

[0091] Materials used for the aforementioned partitions include, for example, glass fiber, cellulose, porous polyolefins, polyamide, and polyester.

[0092] The electrolyte can be either a liquid or a solid, and can also be either aqueous or non-aqueous. However, from the viewpoint of easily achieving sufficient practical performance, an electrolyte solution composed of an electrolyte salt and a solvent is suitable.

[0093] Examples of the aforementioned electrolyte salts include lithium salts such as LiPF6, LiBF4, LiN(SO2F)2, LiN(C2F5SO2)2, LiAsF6, LiSbF6, LiAlF4, LiGaF4, LiInF4, LiClO4, LiN(CF3SO2)2, LiCF3SO3, LiSiF6, LiN(CF3SO2), (C4F9SO2), etc.; metal iodides such as LiI, NaI, KI, CsI, CaI2, etc.; iodide salts of quaternary imidazolium compounds; iodide salts of tetraalkylammonium compounds; perchlorates; and metal bromides such as LiBr, NaBr, KBr, CsBr, CaBr2, etc. These electrolyte salts can be used alone or in combination of two or more.

[0094] As for the aforementioned solvents, there are no particular limitations as long as they do not corrode or decompose the materials constituting the battery, thereby degrading its performance, and can dissolve the aforementioned electrolyte salts. For example, as non-aqueous solvents, cyclic esters such as ethyl carbonate, propyl carbonate, butyl carbonate, and γ-butyrolactone; ethers such as tetrahydrofuran and dimethoxyethane; chain esters such as methyl acetate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; and nitriles such as acetonitrile can be used. One of these solvents can be used alone, or two or more can be used in combination.

[0095] Furthermore, as a solid electrolyte, inorganic solid electrolytes such as sulfide-based solid electrolytes and oxide-based solid electrolytes, or organic solid electrolytes such as polymer-based electrolytes, can be used. By using such solid electrolytes, all-solid-state batteries can be obtained without the use of electrolytes.

[0096] Examples of sulfide-based solid electrolytes include crystalline sulfide (thio-LISICON) materials such as Li₂S-SiS₂-lithium compounds (here, the lithium compound is selected from at least one of the group consisting of Li₃PO₄, LiI and Li₄SiO₄), Li₂S-P₂O₅, Li₂S-B₂S₅, and Li₂S-P₂S₅-GeS₂.

[0097] Examples of oxide-based solid electrolytes include garnet-type oxides such as Li 5La 3M 2O 12 (M=Nb, Ta) or Li 7La 3Zr 2O 12, oxyacid chloride compounds based on the γ-Li 3PO 4 structure collectively known as LISICON, perovskite type, Li 3.3PO 3.8N 0.22 collectively known as LIPON, and sodium / alumina. Examples of polymeric solid electrolytes include polyethylene oxide-based materials, or polymeric compounds obtained by polymerizing or copolymerizing monomers such as hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, ethylene, propylene, acrylonitrile, vinylidene chloride, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, styrene, and vinylidene fluoride. Furthermore, these polymeric solid electrolytes may also contain supporting salts and plasticizers.

[0098] Examples of supporting salts in the aforementioned polymeric solid electrolytes include lithium (fluorosulfonyl imide), and examples of plasticizers include succinate.

[0099] Batteries manufactured using the electrode forming composition of the present invention exhibit superior battery characteristics compared to conventional secondary batteries, even with less fluorinated binder.

[0100] There are no particular restrictions on the form or type of electrolyte of the secondary battery; any form such as lithium-ion battery, nickel-metal hydride battery, manganese battery, or air battery can be used, but lithium-ion battery is preferred. There are also no particular restrictions on the lamination method or manufacturing method.

[0101] When applied to coin-shaped batteries, the electrodes of the present invention described above are simply stamped into a specific disc shape. For example, a lithium-ion secondary battery is manufactured by placing one electrode on a cover body formed by fusing the gasket and spacer of a coin-shaped battery, stacking a similarly shaped separator impregnated with electrolyte on top, and then stacking the electrodes of the present invention from above with the electrode layer facing down, placing the outer shell and gasket on top, and sealing it with a coin-shaped battery riveting machine. [Example]

[0102] The present invention will be described in more detail below with examples and comparative examples, but the present invention is not limited to the examples described below. Furthermore, the apparatus used is as follows.

[0103] (1) Gel permeation chromatography (GPC) (Estimation of weight average molecular weight of fluorinated binders) Apparatus: Prominence high-speed liquid chromatography system manufactured by Shimadzu Corporation. Eluent: 10 mM LiBr in NMP Tube column: Showa Denko (Co., Ltd.), KD-805 Column temperature: 40℃ Detector: Differential refractometer Flow rate: 1 mL / min Sample concentration: 0.1% by mass (20 μL injected) [Determination Method] A diluent was prepared by dissolving 1 mg of the fluoropolymer in 1 mL of N-methyl-2-pyrrolidone (NMP) containing 10 mM LiBr. The diluent was filtered through a filter (polytetrafluoroethylene, pore size: 0.45 μm) to obtain the test sample. The test sample was fed into a gel permeation chromatography (GPC) instrument and the polystyrene-converted molecular weight of the fluoropolymer was determined under the above conditions. The weight average molecular weight (Mw) was calculated.

[0104] (2) Differential scanning calorimeter (DSC) (determination of heat of fusion) Device: NETZSCH, NETZSCH DSC204 F1 Phoenix Sample size: 1.75-2.25 mg Measuring plate: A1 (sealed) [Determination Method] Weigh approximately 2 mg of fluorinated binder into an Al pan and cover it. Perform DSC measurement according to the protocol shown in Table 1 below. Furthermore, in order to eliminate the influence of deviations in the crystallization state of the fluorinated binder, the heat of fusion during the second heating process of No. 6 is used in this invention. Also, in this invention, the so-called heat of fusion is the absolute value of the measured heat of fusion.

[0105]

[0106] (3) Nuclear magnetic resonance (NMR) device (confirmation of polar functional groups) Apparatus: Bruker AVANCE III HD (spectrometer) Bruker Ascend 500 (Magnet) Solvent: Deuterated DMSO (Kanto Chemical) Integration range: 3.20~2.70ppm (integrated values ​​normalized to 100) 2.45~2.10ppm 12.70~12.40ppm Relaxation delay: 1 second Total number: 16 times [Evaluation Method] A very small amount of fluorinated binder was dissolved in deuterated DMSO and NMR was performed. The presence or absence of polar functional groups was confirmed by the presence or absence of a distinct peak detected at 10-15 ppm.

[0107] (4) Homogenizer (for mixing electrode slurry) PRIMIX (stock) manufacturer, TK Robomix (with 2.5mm (φ32) homogenizer / dispersant)

[0108] (5) Thin-film rotary high-speed mixer (mixing of electrode slurry) PRIMIX (stock) manufacturing, Filmix 40 model

[0109] (6) Roller press (electrode compression) Manufactured by TAKUM Corporation, SA-602

[0110] (7) Dry booth SPINDLE Manufacturing Co., Ltd., Japan

[0111] (8) Charge and discharge measuring device Toyo Systems (Co., Ltd.), TOSCAT-3100 Temperature: Room temperature

[0112] (9) Dynamic viscoelasticity measuring device Anton-Paar Corporation manufactures MCR302 and cone plate CP40-1.

[0113] (10) Adhesion and membrane peeling analysis device Kyowa Interface Science (Co., Ltd.), Versatile Peel Analyzer VPA-3

[0114] Furthermore, the raw materials used are as follows. NCM811: Ningbo Ronbay New Energy Technology Co., Ltd., Lithium Nickel Manganese Cobalt Oxide (LiNi 0.8Co 0.1Mn 0.1O 2), "S-800" LFP: Lithium iron phosphate Solef 5140: manufactured by SOLVAY, modified PVdF, Mw 1,033,408 (measured), heat of fusion 32.94 J / g (measured), contains polar functional groups, NMR results are shown in Figure 1. AB: Denka Black (acetylene black, manufactured by DENKA) CNT:FloTube 6120,Jiangsu Cnano Technology Co., Ltd. PAA: Manufactured by Fujifilm and Hikari Pure Chemical Industries, Ltd., Polyacrylic Acid, Mw5,000 PAN: Sigma-Aldrich, polyacrylonitrile, Mw 150,000 Phosphorous acid: Pure Chemicals (stock) AC-10P: Manufactured by Dong-A Synthetic (Co., Ltd.), Polyacrylic Acid, Mw5,000 H-PAN: Made by Dolan GmbH, polyacrylonitrile, Mw200,000 Isobam-18: KURARAY (manufactured), a copolymer of isobutylene and maleic anhydride, Mw 300,000~350,000 Isobam-310: KURARAY (manufactured), a copolymer of isobutylene and maleic anhydride, Mw 160,000~170,000 PVA: Manufactured by Sigma-Aldrich, polyvinyl alcohol, Mw61,000 PLA: Manufactured by Mitsui Chemicals, Inc., Polylactic Acid, Lacea-H100 PEG: Polyethylene oxide manufactured by Alfa Aesar, Mw: 100,000 NMP: Pure Chemical Company, N-methyl-2-pyrrolidone NMP (for GPC): Manufactured by Fujifilm and Koizumi Pure Chemicals, N-methyl-2-pyrrolidone Dehydrated NMP: Manufactured by Kanto Chemical Co., Ltd., N-methyl-2-pyrrolidone, water content below 50 ppm

[0115] [3] Preparation of positive electrode composition (electrode paste) [Examples 1-1 to 1-6, Comparative Examples 1-1 to 1-9] Based on the composition shown in Table 2, active materials, fluorinated binders, conductive carbon materials, compounds containing acidic groups, compounds containing hydrogen-bonded groups, dispersants, and solvents were mixed in a dry chamber. The mixture was homogenized at 8,000 rpm for 1 minute using a homogenizer, followed by two 30-second mixing cycles at a circumferential speed of 20 m / s using a thin-film rotary high-speed mixer to prepare the electrode slurry. The properties and morphology of the resulting electrode slurry were evaluated using the following methods. The results are shown in Table 3.

[0116] [Storage stability of electrode paste] Immediately after the electrode paste was prepared and after standing at 25°C for 3 hours, the loss modulus and storage modulus of dynamic viscoelasticity (frequency-dependent determination) were measured at 25°C with a strain range of 0.1% to 1,000% and a shear rate range of 0.00628 to 62.9 (1 / s). The rate of change of the storage modulus and loss modulus after storage was calculated from the loss modulus and storage modulus measured before and after storage using the following formulas, and judged according to the following criteria. Furthermore, the measured values ​​at 0.1% strain are used in the following calculations. [] Calculation Formula Rate of change of storage elastic modulus (%) = (Storage elastic modulus after 3 hours of resting - Storage elastic modulus immediately after modulation) / Storage elastic modulus immediately after modulation Rate of change of loss elastic modulus (%) = (Loss elastic modulus after 3 hours of rest - Loss elastic modulus immediately after modulation) / Loss elastic modulus immediately after modulation Judgment Criteria 〇: The rate of change of both the storage elastic modulus and the loss elastic modulus did not reach 300%. ×: The rate of change of the storage elastic modulus and the loss elastic modulus is above 300%.

[0117]

[0118]

[0119] [4] Fabrication of the positive electrode [Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-9] Using a scraper, the electrode pastes (freshly made) obtained in Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-9 were uniformly coated onto the aluminum foil (15 μm thick, made by UACJ) of the current collector, dried at 80°C for 30 minutes to form an electrode layer, and then compressed using a roller press to make an electrode.

[0120] [Determination of the adhesion of electrode paste] Electrodes obtained in each embodiment and comparative example were cut to a width of 25 mm. A 20 mm wide double-sided adhesive tape was attached to the coated surface of the electrode composite layer and fixed to a glass substrate. The electrode was then fixed to an adhesion and film peeling analysis device, and a peeling test was conducted at a peeling angle of 90° and a peeling speed of 100 mm / min to measure the adhesion. The test results were judged according to the following criteria. The results are shown in Table 4. Judgment Criteria 〇: The tightness is above 5 N / m ×: Adhesion strength does not reach 5N / m

[0121]

[0122] [5] Battery manufacturing and performance evaluation [Examples 3-1 to 3-6, Comparative Examples 3-1 to 3-7] Four disc-shaped electrodes with a diameter of 10 mm were stamped from the positive electrodes obtained in Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-5, and 2-8 to 2-9. The mass of the positive electrode layer (the mass of the stamped electrode minus the mass of the uncoated portion of the electrode stamped to a diameter of 10 mm) and the thickness of the electrode layer (the thickness of the stamped electrode minus the thickness of the substrate) were measured. After vacuum drying at 120°C for 15 hours, the electrodes were transferred to a drying chamber.

[0123] As the negative electrode, four 13mm diameter disc-shaped electrodes were stamped from an electrode plate (manufactured by (Yayama Corporation)) made with an electrode plate of artificial graphite:carboxymethyl cellulose (CMC):styrene-butadiene copolymer (SBR) in a mass ratio of 98:1:1. The mass of the negative electrode layer (the mass of the stamped electrode minus the mass of the uncoated portion of the electrode stamped to a diameter of 13mm) and the electrode layer thickness (the thickness of the stamped electrode minus the thickness of the substrate) were measured. After vacuum drying at 120°C for 15 hours, the electrodes were transferred to a drying chamber.

[0124] On a cover body with a gasket and spacer of a 2032-type coin-shaped battery (manufactured by Baoquan Chemical Co., Ltd.), a negative electrode is placed with the electrode coating side facing upwards. A mixture of 20g of electrolyte (ethyl carbonate: diethyl carbonate = 1:1 (volume ratio), with lithium hexafluorophosphate dissolved in 1M electrolyte, manufactured by Kishida Chemical Co., Ltd.) and 0.4g of ethyl fluorocarbonate (manufactured by Kishida Chemical Co., Ltd.), stacked on top of each other, is stamped into a 16mm diameter separator (glass fiber circular filter paper GF / F, manufactured by WATT MANN CO., LTD.). The positive electrode is then stacked from above, with the active material coating side facing downwards. After adding one drop of electrolyte, the outer shell and gasket, formed by fusing the gasket and spacer, are placed on top and sealed using a coin-shaped battery riveting machine. After standing for 24 hours, four test secondary batteries are produced.

[0125] [Charge / Discharge Evaluation] The characteristics of the experimental secondary batteries were evaluated. To assess the effect of additives in the positive electrode on the battery, charge-discharge testing was conducted using a charge-discharge measurement device, following the order of battery aging and load characteristics evaluation, under the conditions shown in Table 5. Table 6 shows the design theoretical capacity and the results of charge and discharge capacity under 3C conditions for each battery.

[0126]

[0127]

[0128] As shown in Table 6, the secondary battery with a positive electrode made using the electrode forming composition of the present invention has high battery characteristics even with less fluorine binder.

Claims

1. An electrode forming composition comprising an acidic compound, a hydrogen-bonding compound, a fluorinated binder, a conductive carbon material, and an active substance, wherein the acidic compound is a polymeric organic compound having an acidic group and / or its salt at a content of 15% by mass or more per molecule, or a non-polymeric organic compound having 4 or more acidic groups and / or their salts in a molecule; the hydrogen-bonding compound is a polymeric organic compound having an acidic group and / or its salt at a content of less than 15% by mass per molecule, or a non-polymeric organic compound having 3 or fewer acidic groups and / or their salts in a molecule; the content of the acidic compound is 0.001 to 0.5% by mass of the total solids; and the content of the fluorinated binder is 0.01 to 1.0% by mass of the total solids.

2. The electrode forming composition as claimed in claim 1, wherein the content of the fluorine-based binder is 0.1 to 0.7% by mass of the total solids.

3. The electrode forming composition as claimed in claim 1, wherein the content of the above-mentioned acid-containing compound is 0.01 to 0.3% by mass of the total solids.

4. The electrode forming composition of claim 1, wherein the content of the above-mentioned hydrogen-bonded compound is 0.001 to 0.5% by mass of the total solids.

5. The electrode forming composition of claim 1, wherein the above-mentioned acidic compound is a polymeric organic compound in which the content of acidic group and / or its salt per molecule is 25% by mass or more, or a non-polymeric organic compound having 5 or more acidic groups and / or their salts in a molecule.

6. The electrode forming composition of claim 1, wherein the acidic group and its salt are selected from at least one group consisting of carboxylic acid group, phosphoric acid group, sulfonic acid group and salts thereof.

7. The electrode forming composition of claim 6, wherein the acidic group and its salt are carboxylic acid groups and / or their salts.

8. The electrode forming composition of claim 1, wherein the acid-containing compound is a polymeric organic compound.

9. The electrode forming composition of claim 8, wherein the weight average molecular weight of the acid-containing compound is 250 to 2,000,000.

10. The electrode forming composition of claim 1, wherein the aforementioned hydrogen-bonding compound is selected from at least one group consisting of compounds containing carbonyl groups, compounds containing hydroxyl groups, compounds containing ether groups, compounds containing amine groups, and compounds containing sulfonyl groups.

11. The electrode-forming composition of claim 10, wherein the aforementioned hydrogen-bonding compound is selected from at least one of the following: Polymer-type organic compounds selected from the group consisting of polylactic acid, maleic anhydride polymers, anhydrous maleimide polymers, polyphenols, polyvinyl alcohol, polyethylene glycol, polyethyleneimine, polyether ether, polyether ether and polyaryl ether ether, and copolymers and derivatives thereof containing at least one of these, and non-polymer-type organic compounds selected from the group consisting of maleic anhydride, acetone, citric acid, tannic acid, diethyl ether, tetrahydrofuran, amino acid alanine, aspartic acid, aspartic acid, glutamic acid, serine, arginine, cysteine, glutamic acid, glycine, proline, tyrosine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, sulfonic acid halides, triethylene glycol dimethyl sulfonate, and ethyl p-toluenesulfonate.

12. The electrode forming composition of claim 11, wherein the hydrogen-bonded compound is a polymeric organic compound selected from the group consisting of polylactic acid, maleic anhydride polymer, anhydrous maleimide polymer and polyvinyl alcohol, and copolymers and derivatives thereof containing at least one of the above.

13. The electrode forming composition of claim 8, wherein the acidic compound is a copolymer comprising repeating units: repeating units derived from monomers having groups selected from the group consisting of aromatic rings, alkyl, amino, ether, nitrile, hydroxyl and carbonyl groups, and repeating units derived from monomers having carboxylic acid groups and / or their salts.

14. The electrode forming composition of claim 13, wherein the acidic compound is a copolymer comprising repeating units: repeating units derived from monomers having groups selected from the group consisting of nitrile, hydroxyl and carbonyl groups, and repeating units derived from monomers having carboxylic acid groups and / or their salts.

15. The electrode forming composition of claim 1, wherein the weight average molecular weight of the fluorinated binder is 600,000 to 3,000,000.

16. The electrode forming composition of claim 1, wherein the heat of fusion of the fluorine-based binder, as determined by differential scanning calorimeter (DSC), is 10 to 35.8 J / g.

17. The electrode forming composition of claim 1, wherein the fluorinated binder is modified with polar functional groups.

18. The electrode forming composition of claim 1 further comprises a dispersant.

19. The electrode forming composition of claim 18, wherein the dispersant is a homopolymer of monomers selected from the group consisting of nitrile monomers, aromatic olefin monomers and aliphatic olefin monomers, or a copolymer of two or more such monomers, and the weight average molecular weight is 1,000 to 2,000,000.

20. The electrode forming composition of claim 18, wherein the content of the dispersant is 0.01 to 0.5% by mass of the total solids.

21. The electrode forming composition of claim 1, wherein the active material is an oxide comprising Li and at least one selected from Ni and Fe, or comprises S, and the electrode forming composition is a composition for a positive electrode.

22. The composition for forming the electrode as claimed in claim 1, wherein the loss modulus of dynamic viscoelasticity is greater than the storage modulus after immediate modulation and after standing at 25°C for 3 hours.

23. An electrode having a current collector substrate and an electrode composite material layer formed on at least one side of the current collector substrate, the electrode composite material layer being formed with an electrode forming composition as claimed in any one of claims 1 to 22.

24. An energy storage device having electrodes as claimed in claim 23.

25. The energy storage device as described in claim 24 is an all-solid-state battery.

Images